As used herein, “slurry” means a mixture of solid particles in a liquid, such as solid particles mixed in an oil- or aqueous-based liquid. Such slurries are used in various fields (chemistry, medicine, electronics, ceramics, foods, feed, etc.) and are mixed, kneaded and dispersed to obtain a slurry of finely divided particles dispersed generally uniformly in the liquid.
There have been known apparatuses for a mixing and kneading treatment or a dispersion treatment of slurry as a treatment material, particularly slurry having a low viscosity to a medium viscosity (1 to 100 dPa·s) without using dispersion media (beads or balls). For example, the treatment apparatus described in JP-A-2014-76441 comprises a vessel having a supply port and a discharge port for a slurry treatment material, a rotary body rotatably disposed in the vessel, and an annular fine gap formed between the inner face of the vessel and the outer periphery face of the rotary body and in which the treatment material flows, wherein notches are formed on the surface of the rotary body. The rotary body is in the form of a cylindrical body having projections that extend in the longitudinal direction of the cylindrical body and that are formed at circumferentially spaced intervals on the outer periphery face of the cylindrical body. By using this apparatus, it is possible to finely pulverize solid particles (powder) in the slurry. However, when the solid particles are a mixture of different materials (mixed solid materials) one of which is very fine nano powder, the powder has a tendency to agglomerate into clumps, and therefore insufficient fine pulverization sometimes occurs.
When agglomerates or clumps of powder are formed, it is worth considering the use of a bead mill. However, since the bead mill has such a structure that the treatment material is stirred with dispersion media (beads or balls) in a vessel to disperse the treatment material, the dispersion media may sometimes be abraded or broken by impact or friction caused by the stirring motion. Consequently contaminants formed by the abrasion or the break of the dispersion media may likely be incorporated into the treatment material thereby degrading the quality of the treated material. Particularly, when treating mixed solid particles containing nano particles, the treatment is carried out at a high circumferential speed, which causes the particles themselves to be damaged by the dispersion media, and therefore it has been difficult to homogenize the properties of the treated material. Further, if the temperature of the treatment material is raised during the dispersion treatment, the quality of the treated material is adversely affected.